Astra G 2.5" Front Pipe and Sports Cat..........

M22APW

Finally managed to get the front half of the exhaust done on Saturday. Its been a while mainly due to lack of time and to being flat out at work.

Basically the car is running a 2.5" Milltek Cat Back system so I sourced the required components........ a 2.5" stainless flexi section, a 90 degree bend, a 30 degree bend (both 63.5mm diameter), a length of 63.5mm stainless pipe, 2 lambda bosses, a 2.5" 2 bolt flange and an HJS 200 cpi motorsport cat which I had previously had used elsewhere (hence the reason it looks a little second hand!).

Took the old front pipe off the car (which had previosuly had the pre cat removed). As you can see from the picture my OE front pipe was changed from sleeved fitment and had a 2 bolt flange fitted to it to allow easy fitment of the cat back system.

We cut the 3 bolt flange cut off the OE pipe and then had the following made up using the various sourced bends etc:

And here is the finished front pipe fitted onto the car:

So the car now has a 2.5" system from manifold back including front pipe with no pre cat and an HJS motorsport cat fitted. As I was using the 2.5" cat back system with a 2 bolt flange (same as the turbo cars - removing the usual sleeve fitting at this point which the 2.2 cars usually run) we simply fabricated to the 2 bolt flange to meet it, making fitting really simple!

The car does sound more throaty now and more responsive and it is now back on the dyno to see what difference it has made before final mapping (at long last!)

JohnnyN

Good work Mark. That pipe looks great!

;-)

vocky

that's a decent downpipe 😃

just need to replace the cast manifold now :roll:

I can't really advise you to buy a tms 4-1 or regal 4-1 can I :lol:

Matt

Looks great Mark, what sort of increase are you expecting?

M22APW

vocky said:
that's a decent downpipe 😃

just need to replace the cast manifold now :roll:

I can't really advise you to buy a tms 4-1 or regal 4-1 can I :lol:

Thanks. Pleased with the results. One of the guys locally is a very good stainless welder/fabricator! Not considering changing the manifold to be honest. On the S/C car the manifold isn't a major problem....... the Stage 2 where I'm at produces enough power and torque without the need for a different manifold (for which I cannot justify the cost). We know the conversion is durable at this level, so adding something that could put it outside its durability window wouldn't be sensible. The Stage 3 (under development) in VX220 is capable of up to 300 bhp on the OE manifold.......... so unless I want to start engine rebuilding and such like to achieve this, the car is to all intent and purpose finished 😃 (oh and loads of fun to drive too

Matt said:
Looks great Mark, what sort of increase are you expecting?

It should tip it comfortably into the mid 240's as the S/C VX220's do that on a 2" system with sports cat and no pre cat. Will let you know as one evening we will run the car on the dyno to see the difference from the downpipe/cat assembly and then finish off the mapping.

vocky

if you used a better exhaust manifold you wouldn't need to tweak the engine so much dunno..

it's worth trying one to see what the gains would be, a na engine gains 10 bhp from the manifold on it's own 🙂

M22APW

vocky said:
if you used a better exhaust manifold you wouldn't need to tweak the engine so much dunno..

But the engine has been supercharged to provide the increase in power and torque....... I couldn't tweek it any less with this converson and certainly for the money I've spent, I couldn't have got the same power/torque from any other tuning method on this engine.

vocky said:
it's worth trying one to see what the gains would be, a na engine gains 10 bhp from the manifold on it's own 🙂

When we did the original development on the S/C conversion we did look at different manifolds.......... but if any increase puts the engine outside of what we consider is safe and durable and then there is a potntial for failure this wouldn't be good.

We know the S/C conversion is duarable on standard internals at the power level on Stage 2 WITHOUT any internal engine mods. If we go above this power level and run the risk of breaking components this will not be good for our customers, our conversions or our repuatation. Hence we undertake thorough development and release conversions which we know are durable. There are enough S/C conversions in the UK, Europe and Norway to prove this. Granted there is potentially more power/torque available from the Stage 2 but commercially if we do it and it breaks on a customer it looks bad for everyone....... We know the only safe way we can get more power is to strengthen internals.

vocky

You guys at Courtenay do a fantastic job of the sc conversion, but there's more to come from the sc than 250 bhp, 300bhp+ is where it should be 8)

I would love to build the ultimate sc conversion for my vectra 🙂

my spec would be similar to what NickB is planning 8)

bottom end
eagle rods
wiseco pistons
balancer shaft delete kit

head
stage three ported - GM / Patriot
standard size wasted stem valves
standard cams

Inlet
GM sc kit
GM stage two upgrade kit
charge cooler
68mm 2.0 sc tb
matching intake system

exhaust
Regal 4-1 manifold (it looks a better design for forced induction, the tms 4-1 suits na)
100 cell sports cat
3" system

ecu

Emerald

vocky

just found this on a usa site, not good news for sc owners 🙁

The reason that the #4 piston melts around 280ish is the supercharger itself. Most of the ppl that have blown up were running under 2.7 pullies which is simply way out of the specs for max rpm on the blower. Also many were careless and didnt upgrade the heat exchanger which is a virtual must when going smaller than the stock pulley as well as not taking advantage of water injection. Also blower porting for Stagmier (sp?) helps out a ton with IATs. Its also been confirmed that the intake manifold is poorly designed and flows significantly more air to the #4. This is why from the factory and with GM stage 2 they are pig rich, its done to keep things safe. Most of the folks with blown engines were running 11:8 or higher on air fuel. Obviously your wideband is a collective reading of all 4 primaries so you never realize theres a problem with an individual cylinder. The problem can be corrected with a stand alone that allows for different fueling per cylinder. Sadly thats just not something you can do with HP tuners

M22APW

vocky said:
300bhp+ is where it should be 8)

So that will be the Stage 3 that we have under development then!

jsulen

Installing your Astra G 2.5" Front Pipe and Sports Cat looks great. Any changes with your car's performance?